Mark Zuckerberg, right, and Andrew Houston, founder and chief executive of Dropbox, wait in a parked car for the traffic to clear out at the Sun Valley Lodge during the Allen & Company Sun Valley Conference last week.

But if you were a billionaire with flexibility you could probably be paying a lot less. Case in point, reports Bloomberg, Mark Zuckerberg, the billionaire CEO and founder of Facebook, just refinanced his $5.95 million mortgage with a 30-year adjustable-rate loan that begins with a 1.05 percent interest rate.

The reason for that incredible rate is that it can change month to month and Zuckerberg, with a $15.7 billion net worth, can afford to take that risk.

So why would Zuckerberg even need a mortgage? Here's Bloomberg:

"While almost all lending rates have reached historical lows this year, the borrowing costs available to high-net-worth individuals are even lower if the person is willing to bear the risk of monthly interest rate adjustments, said Greg McBride, senior financial analyst with Bankrate Inc., a North Palm Beach, Florida-based firm that tracks interest rates. Large increases are unlikely anytime soon with the Federal Reservesignaling it will keep interest rates near zero for at least two years.

"'When you can borrow at a rate below inflation, you're borrowing for free,' McBride said in an e-mail. 'This is the concept of using other people's money and it preserves financial flexibility for the borrower.'"